Antenna having at least two radiators fed with different phase



NOV. 26, 1968 L ET AL ANTENNA HAVING AT LEAST TWO RADIATORS FED WITHDIFFERENT PHASE 3 Sheets-Sheet 1 Original Filed Nov. 21. 1962 Main FeedLine "Sourcz ANTENNA HAVING AT LEAST TWO RADIATORS FED WITH DIFFERENTOriginal Filed Nov. El, 1962 PHASE 5 Sheets-Sheet 2 NOV. 26, 1968 LAUBET AL 3,413,644

ANTENNA HAVING AT LEAST TWO RADIATORS FED WITH DIFFERENT PHASE OriginalFiled Nov- 21. 1962 :5 s -s 3 United States Patent 3,413,644 ANTENNAHAVING AT LEAST TWO RADIATORS FED WITH DIFFERENT PHASE Helmut Laub andClaus Hoyer, Munich, Germany, aS- signors to Siemens Aktiengesellschaft,Munich, Germany, a corporation of Germany Continuation of applicationSer. No. 240,200, Nov. 21, 1962. This application Sept. 7, 1967, Ser.No. 666,216 Claims priority, application Germany, Nov. 23, 1961,

S 76,808, S 76,809, S 76,810 12 Claims. (Cl. 343800) ABSTRACT OF THEDISCLOSURE An antenna arrangement having a relatively circular radiationpattern in the transmission range, employing at least three radiatorswhich are fed with different phasing and enclose, in the basearrangement, respective angles between their main radiation directions,in which between one radiator pair, on a change in the frequency, thereoccurs an increase, and between another radiator pair a decrease in thedifference in the feed phases, the angles between the main radiationdirections of adjacent radiators being such that radiators, betweenwhich the difference in the feed phases becomes greater with increasingfrequency, enclose a greater angle between their main radiationdirections than those radiators between which the difference in the feedphases becomes less with increasing frequency.

This is a continuation of application Ser. No. 240,200, filed Nov. 21,1962, now abandoned.

The invention disclosed herein is concerned with an antenna arrangementcomprising at least two radiators or radiator groups which arerespectively fed with different phase signals.

It is known to feed different loads or antenna radiators with differentphase signals, such that the respective reflective energy components onthe lines are cancelled in the direction of the energy source. Such anarrangement results, with appropriate dimensioning of the feed linesextending to the individual loads, in an improved matching with respectto the common feed line.

The feed of the radiators in the above described manner results in adisadvantage in the case of antenna arrangements, namely, that there isa distortion of the radiation pattern due to the components of theenergy which are radiated with different phases. Such distortion may becompensated in a known manner by spatially displacing the antennaradiator elements in accordance with the different feed phase. In thecase of a directional antenna which comprise two radiators arranged on astraight line, and which radiators are fed with signals having a phasedifference of 90 and wherein the principal radiation directions of whicharethe same, the radiator fed with lagging phase is accordinglydisplaced in the radiation direction by M4, whereby the distortion ofthe radiation diagram which is caused by the phase shift, is practicallycancelled. The spatial displacement of the radiation center points,referred to the principal radiation direction, is likewise M4. Theradiation diagrams of such spatially displaced radiator arrangementscorrespond substantially to those obtained with radiators which are fedwith the same phase.

It is known to use a plurality of individual antennae in appropriategrouping, for example, in the form of dipole fields, so as to obtain asector-like or circular radiation diagram. The simplest examples ofantennae of this kind are represented by dipole fields arranged on thesides of a mast, such fields being in the case of an omnidirectionalradiation diagram uniformly distributed about the Patented Nov. 26, 1968mast; in the case of a sector-like radiation diagram, all sides of themast are not provided with dipole fields. If it is desired, inconnection with such antenna arrangements, desired to make use of thephase shifted feed of the radiators, there must be effected, in theradiating plane of the system, a displacement of the radiation centerpoints so as to obtain a compensation of the distortion caused by thephase shifted feed. Accordingly, in the case of four dipole fieldsarranged respectively with phase difference on the sides of a squaremast, the total displacement of the radiation center points of tworespective dipole fields, referred to the half angle line of theprincipal radiation directions, amounts to A/ 4. Therefore, theradiation center points must be displaced by A/4. /2 along therespective side of the mast. The displacement of the radiation centerpoints refers to the half angle line between the principal radiationdirections because, with identical phase feed of the two radiators, theradiation components will likewise superpose in identical phase in thecorresponding direction. The wave length to which this displacement isrelated corresponds to the frequency which is to be radiated. However,upon transmitting a greater frequency band, there will again appeargreater breaks in the radiation diagram, resulting from the fact r thatthe means serving for the production of different feed phases, forexample, cables of given length, donot produce at the input of theradiators the desired phases for other frequencies. Moreover, thespatial displacement, and therewith the compensation of the distortionsof the radiation diagram caused by the phase shift, does not apply atother frequencies. The spatial displacement and the antenna arrangementsthereby obtained are accordingly of narrow band character insofar as theuniformity of the radiation diagram is concerned.

The principal object of the invention is to avoid these drawbacks of theknown arrangements and to render the radiation diagrams more uniformover a broad band, even in connection with antenna arrangements havingradiators fed with different phase.

According to the invention, this object is achieved in connection withan antenna arrangement having at least two radiators fed with differentphase, by so disposing the radiators that the main radiation directionsof the radiators in which the phase difference between the feed phasesbecomes greater with increasing frequency, embrace with each other anangle which is greater than the angle embraced by the main radiationdirections of radiators in which the phase difference of the feed phasesdecreases with increasing frequency.

This invention makes it possible to produce radiation patterns whichexhibit over a greater frequency range smaller field strengthfluctuations, whereby the non-circularity of the radiation pattern canbe reduced within a given band width, and wherein the transmittedfrequency range can be extended in the presence of given non-circularityof the radiation diagram. These advantages are obtained in connectionwith omnidirectional radiation diagrams as well as in connection withsectorlike radiation diagrams.

It may be mentioned at this point that antenna arrangements are knownwhich are fed in a rotary field, that is, wherein the radiators, whichare arranged on the sides of a square mast, are respectively rotated bya definite angle which is, however, identical for each radiator. Such anantenna arrangement is likewise narrowband, so far as the transmissiblefrequency range is concerned, since the angles between the mainradiation directions of the individual radiators, even after therotation, are always the same, there being in the disposition thereof nofurthef consideration with respect to the phase conditions in the senseof the present invention.

The invention can be applied to omnidirectional antennae having agreater number (n) of radiators fastened in polygon arrangement on amast or the like. In this instance the phase differences between theindividual radiators correspondingly amount to 360/ 11 degrees, in amanner so as to provide for an angle embraced by the main radiationdirections of successively placed radiators, which is with increasingphase difference at increasing frequency, in excess of 360/11 degrees.Conversely, the angles between the main radiation directions ofsuccessive radiators which result with increasing frequency indecreasing phase differences, are correspondingly selected so as to besmaller than 360/11 degrees.

In connection with antennae operating with phase shifts of 180 or more,which is as a rule the case with antennae arrangements which are fed ina rotary field, the phase shifts of 180 are appropriately produced bychanging the polarity of the feed lines of the respective radiators,while phase shifts greater than 180 are produced by change of polarityand further measures, for example, by insertion of cable portions ofappropriate length. This measure permits further improvement in theuniformity of the radiation diagram.

It is in accordance with another feature of the invention possible toachieve a radiation diagram which exhibits even greater broadbanduniformity, by carrying out the spatial displacement of the radiators,which serves to equalize distortions caused by the different phases.This will provide a spacing between those radiation center points atwhich the difference of the feed phases increases with increasingfrequency, which spacing is greater than that provided between theradiators in which an increasing frequency causes a decrease of thedifference of the feed phases.

However, in connection with known antenna arrangements operated toequalize the phase shift with spatially displaced radiators, the spatialdisplacement of the radiators is so effected that the spacing of theradiation center points remains approximately the same ahead of and inback of the displacement. The non-uniform spacings of the radiationcenter points result in more uniform radiation diagrams over a greaterfrequency range, making it possible to obtain, at constant band width, aslight noncircularity of the radiation diagram, while the transmissiblefrequency range is, with given non-circularity, extended. This resultsin the case of transmitter antennae, for example, for the radiation oftelevision programs, in the advantage of making the reorientation of theantennae unnecessary incident to a change of channel within a band. Theinvention is in the same manner advantageously applicable in the case ofsector-like radiation patterns and in the case of omnidirectionalradiation diagrams.

A further improvement, in the sense of a more uniform broadbandradiation pattern, can be obtained by referring the spatial displacementof the radiators, which serves to compensate or compensation fordistortions caused by the different phases, of frequencies lying abovethe center frequency of the frequency band which is to be transmitted.The amount of the spatial displacement, known as such, of the radiatorsreferred to the center frequency, is normally selected so that there iseffected in the direction of the half angle line between the mainradiation directions of two adjacent radiators, a superposition ofradiation pattern in identical phase. However, the radiation pattern ofan antenna arrangement, obtained in this manner, at greater deviationsfrom the center frequency, exhibits stronger gaps or breaks which can becompensated in broadband manner, by appropriately smaller displacement.The center frequency is thereby determined by the condition whichrequires that the differences of the feed phases reach the values whichare therefor de-, sired. Accordingly, upon producing the phasedifferences by means of cable portions, the lengths of such portions arerelated to or referred to the wavelengths corresponding to the centerfrequency. In the case of antennae with radiators arranged in a plane ina polygon and operating with rotary field feed, the difference betweenthe feed phases amounts to 360/11 degrees (which is the desiredoperating value).

Further details of the invention will appear from the description whichis rendered below with reference to the accompanying drawings showingembodiments thereof.

FIG. 1 shows an antenna arrangement fed with the same phase;

FIG. 2 indicates an omnidirectional antenna with individual radiatorswhich are rotated in the respective main radiation direction thereof;

FIG. 3 represents an omnidirectional antenna with different spacing ofthe radiation center points;

FIG. 4 illustrates an omnidirectional antenna with different spacing ofthe radiation center points and with the radiators rotated in therespective main radiation direction;

FIG. 5 indicates an antenna with spatially displaced radiators forcompensating the phase differences;

FIG. 6 shows an antenna with slight spatial displacement of theradiators; and

FIG. 7 is a perspective view of a radiator group comprising two dipolefields.

The antenna shown in FIG. 1 comprises two radiators or radiator groups 2and 3 which are arranged on two sides of a mast 1, the radiators beingin this case constructed as full wave dipoles and being disposed infront of a reflector wall respectively indicated at 4 and 5. Theradiation center points of the respective radiators are indicated bynumerals 6 and 7, such center points lying symmetrically with respect tothe terminal points of the radiators and in the region between theseterminal points and the respective reflector wall 4 and 5. Antennaearrangements of this kind are known and are used especially in cases inwhich the feed of the individual radiators is effected with the samephase. Upon feeding the radiators with different phase signals, forimproving the matching of the signals, there will be obtained aradiation pattern which differs from the one obtained when the signalsare in the same phase, such different radiation pattern differingtherefrom especially by having a different main radiation directionwhich lies approximately in the direction H.

In the arrangement indicated in FIG. 2, there are provided, on the sidesof the mast 10, dipole fields 12, 13, 14 and 15 comprising respectivelyfull wave dipoles disposed in front of a reflector wall. If theindividual radiators are fed with the same phase (not shown), the dipolefields, corresponding in such case to the fields 12 to 15, are soarranged with respect to the mast that they lie symmetrically withrespect to the individual sides of the mast, the longitudinal axes ofthe radiators thus extending parallel to the side planes of the mast 10.In the case of phase sifted feed signals in a rotary field, wherebythere is a phase difference of 360/11 degrees between the respectiveradiators, resulting with 11:4 in degrees, the radiators are, in knownmanner, shifted or displaced so that the distortions caused by the phaseshifted signals are cancelled. In the arrangement illustrated in FIG. 2,there is for this purpose customarily applied a longitudinaldisplacement or shifting (along the side of the mast), amounting to A /4/2. The wave length A thereby corresponds to the frequency 112, forwhich the difference of the feed phases between the radiators amountsexactly to 360/11 degrees. The indicated shifting by A /4 /2 results, inthe direction of the half angle line between the main radiationdirections, in a displacement of A /4, so that the radiations superposein the same phase. The omnidirectional radiation pattern therebyobtained corresponds to the pattern of a radiator arrangement which isfed with signals of the same phase. The shifting or displacement of theindividual radiator elements is thereby appropriately effected withreference to the radiation center points of the respective dipole field,the term radiation center point indicating the point at which theradiator may be conceived as being concentrated in punctiform manner or,expressing it another way, the point from which the entire radiation is,for the remote field, radiated in an angular range as great as possible.This radiation center point lies in the illustrated antenna arrangementsin the region between the radiators and the reflector wall midwaybetween the radiator halves. The radiation center points of theillustrated dipole fields 12 to 15 lie, in the case of feed with thesame phase at the points 16, 17, 18 and 19, symmetrically to the mast,while lying in the case of phase shifted feed (rotary field), at thepoints 20, 21, 22 and 23, owing to the spatial displacement efiected forthe compensation of the different phases. Upon transmission of greaterfrequency ranges, causing a deviation from the center frequency, thereoccur in this known kind of radiator arrangement deep breaks, valleyseparations, in the radiation pattern, the smallest values of E/E mmthereby lying at 0.5 for a frequency range of 1=0.85 to f=l.18f (f=center frequency). The dipole fields 12 and 14 are for the broadbandequalization of these breaks rotated by the angle a counter to thecenter rotation of the rotary field feed, the radiation center points 20and 22 being thereby used as points of rotation. It is thereby assumed,for the feed of the individual radiator, that the phases 0, 90, 180 and270 are respectively allocated to the dipole fields 12, 13, 14 and 15.These phase differences are appropriately produced by allocating to thedipole fields 12 and 14 feed cables of the same length, the dipole field14 being thereby connected with opposite polarity. The leads to thefields 13 and 15 are shorter by A /4 and the feed line to the fields 13and 15 are likewise of opposite polarity. As a consequence, thedifferences of the feed phases between the fields 12 and 13 as well asbetween 14 and 15 increase with increasing frequency, while thosebetween the fields 13 and 14 as well as between 15 and 12 decrease.Accordingly, the main radiation directions of the first named group offields mutually embrace a greater angle than those of the second group.The displacement of the dipole fields 12 and 14, by the angle 0:,results in an omnidirectional radiation pattern with maximum breakslying in the range 0.857 to 1.18f above the value E/E =0.5.

In FIG. 3, there are arranged on the sides of a mast 31 the dipolefields 32, 33, 34 and 35 comprising respectively full wave dipolesdisposed in front of a reflector wall. The radiation center points ofthe dipole fields are indicated at 36 to 39. As a radiation center pointis designated the point at which the respective radiator or dipole fieldcan be conceived as being punctiform concentrated of, expresseddifferently, at which the total radiation, considered for the remotefield, is in the same phase radiated in an angular range which is asgreat as possible. Accordingly, the radiation center point lies in theillustrated radiator arrangement symmetrical to the respective radiatorhalves and in the range between the corresponding radiators and thereflector wall. In such an antenna arrangement with four radiator fieldsdisposed on the sides of a square mast, there is normally made use ofthe rotary field feed, that is, there is provided a phase differ ence of90 between the respective radiators. The phase step generally amounts inthe case of n radiators disposed in a plane about a mast, to 360/11degrees. In order to equalize the breaks in the radiation diagram, whichare caused by the different phases, the radiators are in known mannershifted along the sides of the mast, so that the radiation patterns ofadjacent fields superpose again in phase between both radiatorsapproximately in the region of the half angle line between the mainradiation directions. A displacement along the sides of the mast,amounting for each radiator field to A/4- /2, results in the illustratedarrangement for a uniform spatial shifting. The spacings of theradiation center points remain thereby,

in the known arrangements, after the shifting, constant,

such spacings corresponding approximately to the values such as areprovided with feeding all radiators with the same phase. The positionsof the radiation center points, resulting from signals of the samephase, are indicated by numerals 36, 40, 38 and 41, the connection linesbetween these points forming a square.

In the illustrated antenna arrangement, the feed of the radiators iseffected by allocating to the dipole field 32 the phase 0, to the dipolefield 33 the phase to the dipole field 34 the phase and to the dipolefield 35 the phase 270. It is thereby assumed that the feed phase of180, for the dipole field 34, is produced by change of polarization ofthe feed lines and that feed cables of the same length are provided forthe fields 32 and 34. The feed cables for the fields 33 and 35 areshorter by x/ 4 and the connections for the field 35 are additionally ofchanged polarity. As a consequence, the phase difference between thedipole fields 32 and 33 will become greater than 90 at a frequency whichis higher than the center frequency f for which the cable lengths aredesigned, while the phase difference between the dipole field 33 and thedipole field 34 assumes correspondingly smaller values, since the phaseangle of 180 for the dipole field 34 is produced by change of polarity,therefore being independent of the frequency. The phase differencebetween the dipole field 34 and the dipole field 35 becomesprogressively greater than 90, while the phase difference between thedipole field 35 and the dipole field 32 becomes progressively smallerthan 90.

Upon arranging the radiators in the heretofore customary manner, withthe radiation center point constant at about a there will result breaksin the radiation diagram going in the range of 0.85 to l.l5f down to avalue E/E =0.5. The transposition or displacement of the radiationfields, so that the spacing of the radiation center points of the dipolefields is increased with increasing phase difference between theradiators and correspondingly decreased with decreasing phasedifferences, results in the illustrated radiation pattern in which themaximum breaks at the same frequency range go only down to the valuesE/E .=0.5 6, as seen in FIGURE 3. The spacing d between the radiationcenter points 36 and 37 as well as the radiation center points 38 and 39thereby amounts to about 1.251,, while the spacing d respectivelybetween the points 37, 38 and 39, 36 amounts only to 0.75a The radiationdiagram is plotted for the various frequencies, the full line curve 42indicating the course at f=f the dash line curve 43 the course at f=085fand the dot-dash curve 44 the course at f=l.18f

The change of position of the radiators can be effected in various ways,for example, by shifting both or only one of adjacent radiators. Thedisplacement of the radiation center points for the illustratedradiation pattern amounts to about 7\ /4, in the direction of the anglehalf line between the main radiation directions, where corresponding tothe center frequency f,,,. A further improvement in the uniformity ofthe radiation pattern is obtained upon making this displacement smallerthan A /4. Expressed in other words, this means, that the displacementis referred to a frequency which is higher than f FIG. 4 shows anantenna arrangement for producing an omnidirectional radiation diagram,comprising dipole fields 51, 52, 53, 54 disposed on the sides of asquare mast 50, said dipole fields consisting respectively of full wavedipoles arranged in front of a reflector wall. The radiation centerpoints of the dipole fields are indicated by numerals 55, 56, 57 and 58,it being assumed that the feed of the radiators is effected in themanner explained in connection with FIG. 1 and that the phase 0 isallocated to the dipole field 51, the phase 90 to the dipole field 52,etc. The dipole fields 51 and 53 are, as described with reference toFIG. 1, in the main radiation directions thereof rotated by the angle 0twith respect to the sense of rotation of the rotary field, therebyproviding the improvement of the radiation diagram explained inconnection with FIG. 1. The spatial displacement or shifting withrespect to the side planes of the mast is differently effected inaddition to the rotation of these dipole fields. This results indifferent spacing between the radiation center points of the individualdipole fields, the spacing at, between the radiation center points ofthe dipole fields 51, 52 and 53, 54, respectively, and the spacing dbetween the radiation center points of the dipole fields 52, 53 and 54,51, being so selected that d /d =1.15. The selection of these differentradiation center point spacings is governed by the rule according towhich greater radiation center point spacings are proviided for phasedifferences which increase with increasing frequency, while smallerspacings are provided for those radiation center points between whichthe phase difference becomes smaller with increasing frequency.

Based upon the mode of feed of the radiators, to be presently describedwith reference to FIG. 5, the phase difference between the dipole fields51, 52 and 53, 54 becomes greater with increasing frequency, whilesmaller phase differences appear, between the dipole fields 52, 53 and54, 51 with increasing frequency. The spatial displacement of theradiation center points or the shifting thereof along the sides of themast provides an improvement of the omnidirectional radiation pattern,which is less than in the known arrangements. The displacement isnormally so effected that the radiation of the individual dipole fieldssuperpose approximately with the same phase, approximately in the regionof the half angle line between the dipole fields at the center frequencyf This results, for example, in the case of square masts and dipolefields fed in rotary field with 90 phase difference, in a displacementalong the sides of the mast, amounting to A /4- /2. With reference tothe half angle line, there is obtained a total displacement amounting to025%,. However, for obtaining a more uniform broadband omnidirectionalradiation pattern, there is in the present case effected a displacementamounting only to 0.22 Expressed in other words, this means, that thefrequency corresponding to the spatial displacement of the radiationcenter points is approximately 1.14 and not the center frequency f Theangle for the rotation of the main radiation directions of the dipolefields 51 and 53 amounts to 5".

The resulting radiation diagram is for various frequencies likewiserepresented in FIG. 4 in conjunction with the antenna arrangement. Thefull line curve 59 shows the course of the field strength for thefrequency 0.85f the dash line curve 60 indicating the course for thefrequency f and the dot-dash curve 61 representing the course for thefrequencies f=l.18f Considerably shortened full wave dipoles with aratio of length to diameter of about 15, disposed in front of areflector wall, were used in the illustrated antenna arrangement.Accordingly, as compared with customarily constructed antenna, fed in arotary field and having spatially simply displaced radiators, thedeepest breaks of which extend for the same frequency range up to thevalue E/E =0.5, there is obtained a considerably more uniform fieldstrength curve, making it possible to transmit with the antennaarrangement and given nor1circularity of the radiation diagram, agreater frequency range.

As illustrated in FIG. 7, in order to obtain a sharply focused verticalcharacteristic, a plurality of dipole fields 12 may be arranged, inknown manner, in vertical succession in front of a reflector wall 4' toform a radiator group, thereby employing in the vertical direction themeasures utilized as described in connection with the horizontaldirection.

Referring to the arrangement shown in FIG. 5, it is assumed that theradiator 62 is fed with advancing phase as compared with the radiator63. For the equalization of this phase difference, there is used inknown manner a spatial displacement of the radiators, such that theamount of the spacing d of the radiation center points in the directionH of the half angle line between the main radiation direction of theindividual radiators 62 and 63, corresponds to phase differenceexpressed in terms of wave length. Accordingly, when the two radiators62 and 63 are fed with a phase difference, the spatial displacement willamount to d= \/4. Upon maintaining the spacing D of the radiation centerpoints perpendicularly to the main radiation direction, this antennaarrangement will have the same base width as the arrangement shown inFIG. 1 and therefore will result substantially in the same radiationdiagram except for negligible alterations in the side fractions of theradiation. Upon transmitting a wider frequency band, the spacing d ofthe radiation center point was so selected, that the phase shift betweenthe radiators, with reference to the center frequency f was cancelled bythe spatial displacement. As compared with this, the invention providesfor a spatial displacement, such that the spacing d corresponding to awave length which, in turn, corresponds to a frequency lying above thecenter frequency of the frequency band to be transmitted. Expressed interms of length, this means that the spacing d is to be smaller than incase of the customary matching to the center frequency.

FIG. 6 shows an antenna arrangement for omnidirectional radiation andthe corresponding radiation pattern for various frequencies. Thisantenna arrangement was constructed with shortened full wave dipoleswith a ratio of length to diameter of about 15, with the respectivedipoles disposed by about 0.28% in front of planar reflectors. Thespacing D between the radiation center points 70, 71, 72, 73 of the fullwave dipole fields 74, 75, 76, 77, corresponded approximately to thewave length of the center frequency of the frequency range which is tobe transmitted. The feed of the dipole fields 74 to 77 was effected withthe phase 0 for the field 74, 90 for the field 75, the phase for thefield 76 and the phase 270 for the field 77. In the case of n fields,there generally applies for the phase step Ago from one to the otherradiator, the relation A =360/n degrees. Feed cables of identical lengthwere, for the production of the phase steps, assigned to the dipolefields 74 and 76 and the terminal points at the field 76 were changed inpolarity (corresponding to the 180 phase difference). The leads for thefields 75 and 77 were shorter by A /4 than those for the fields 74 and76, and the polarity for the field 77 was additionally changed. Theselengths correspond to the center frequency f,,,. Upon shifting theradiation center points so that the resultant spatial displacementamounts, for the equalization of the phase shift at the center frequencyin the direction of the half angle line, to k t, there will be obtaineda radiation pattern with border values lying between E/E 1.O and E/E=O.5. Upon using for the production of the phase shifts, in place of thedescribed feed mode, cable portions of x /4, X /Z and 3)\ /4, that is,without change of polarity, there will be reached at the deepest breaksin the radiation diagram even values extending down to E/E =0.4. Thegiven values apply with the assumption that the transmitted frequencyrange lies between f=0.85f and ;f=l.18f whereby f corresponds to thecenter frequency formed by the geometric mean of the highest and lowestfrequency of the frequency range which is to be transmitted;

As contrasted with this, the illustrated radiation pattern show thedirection of the field strength resulting upon shifting the dipolefields by only 0.77 times the value which corresponds to a displacementreferred to the center frequency i In terms of the wave length, thismeans, that the frequency to which is referred the spatial displacement,has the value f /0.77=1.3-f Accordingly, the spatial displacement of theradiators is in case of the illustrated antenna arrangement referred toa frequency which is outside the frequency range to be transmitted,

which frequency reaches in the present case its upper limit at f=1.18fIn the illustrated radiation pattern, the full line curve 78 correspondsto the frequency f=0.85f the dash line curve to f=f and the dot-dashcurve 80 to f=l.18f In the illustrated antenna arrangement according tothe invention, the maximum breaks therefore lie above the value E/E =0.5which results as the deepest break in the case of a displacementreferred to the center frequency and operating with the same mode offeed.

The invention is not inherently limited to the described and illustratedantennae arrangements but may likewise be applied in cases of larger orsmaller numbers of radiators disposed on a mast. Moreover, in the caseof plural tier antenna arrays, there may be used a mechanical rotationof two respective superposed omnidirectional units, by 90, withcorresponding phase shifted feed. The shifting or displacement of theradiator elements, in a horizontal plane, may be analogously applied inthe case of vertically stacked radiators fed with different phase, so asto obtain vertical radiation diagrams which likewise are to be asuniform as possible in a greater frequency range.

Changes may be made within the scope and spirit of the appended claimswhich define what is believed to be new and desired to have protected byLetters Patent.

We claim:

1. An antenna arrangement having a relatively circular radiation patternin the transmission range, comprising at least three radiators which arefed with different phasing and enclose, in the base arrangement,respective angles between their main radiation directions, in whichbetween one radiator pair, on a change in the frequency, there occurs anincrease, and between another radiator pair a decrease in the differencein the feed phases, the angles between the main radiation directions ofadjacent radiators being such that radiators, between which thedifference in the feed phases becomes greater with increasing frequency,enclose a greater angle between their main radiation directions thanthose radiators between which the difference in the feed phases becomesless with increasing frequency.

2. An antenna arrangement according to claim 1, having n-number ofradiators fed in progressive phasing, for the production of anomnidirectional radiation diagram, wherein the radiators at which thephase differences increase with increasing frequency form with theirmain radiation directions an angle greater than 360/n degrees, the anglebetween the main radiation directions of radiators between which thephase difference decreases with increasing frequency, being smaller than360/ n degrees.

3. An antenna arrangement according to claim 1, wherein the phaseshifting is, upon using phase angles of 180, obtained by change ofpolarity of the feed, and in case of greater phase angles additionallyby the use of cable portions of appropriate length.

4. An antenna arrangement according to claim 1, wherein distortions ofthe radiation diagram, caused by different phases, is compensated byspatial displacement of the radiators, such that the spacing betweenthose radiation center points the phase difference of which increaseswith increasing frequency, is greater than in the case of radiators atwhich an increasing frequency causes reduction of the phase difference.

5. An antenna arrangement according to claim 1, wherein the spatialdisplacement of the radiators is referred to a wave length whichcorresponds to a frequency lying above the center frequency of thefrequency band which is to be transmitted.

6. An antenna arrangement according to claim 3, wherein the length ofcable portions employed for the phase shifting is related approximatelyto the center frequency of the transmitted frequency range, therebyeffecting at such frequency the desired distribution of the phasedifferences between the respective radiators.

7. An antenna arrangement according to claim 1, wherein the radiatorsare combined to form radiator groups at the respective inputs of whichappear the desired phase relations.

8. An antenna arrangement according to claim 1, forming anomnidirectional antenna, comprising radiators uniformly disposed about amast and fed with a rotary field.

9. An antenna arrangement according to claim 4, comprising four dipolefields disposed at the sides of a square mast, the spacing betweenadjacent radiation center points d, and d lying approximately at d /d=1.15.

10. An antenna arrangement according to claim 4, for transmitting a bandwidth of about 0.85 to 1.18f (f =center frequency), wherein the spatialdisplacement of the radiators is referred to a wave length correspondingto a frequency 1.l4f

11. An antenna arrangement according to claim 4, comprising fourradiators disposed on the sides of a square mast and fed in a rotaryfield, wherein the deviation from the angle between main radiationdirections, given by the requirement 360/14 degrees (n=number ofradiators), amounts respectively to 5.

12. An antenna arrangement according to claim 4, wherein the rotation ofthe radiators is effected about the radiation center point as an axis ofrotation.

ELI LIEBERMAN, Primary Examiner.

